Since there is no suitable method for processing plano-convex quartz oscillators they have seldom been put to practical use although a few large-sized oscillators of this kind have been used. According to one of the conventional methods of processing this kind of quartz oscillators, they are polished by hand or quartz pieces are applied by the fingers to a concave spherical lapping dish to be processed. Such processing by hand is inefficient and results in increased cost. In such processing by hand it is difficult to achieve uniform polishing. Moreover, there is the possibility that uneven polishing may result in spoiling the cut angles of the quartz blank. This results in deterioration in the temperature characteristics of the oscillator. The conventional methods of polishing plano-convex quartz oscillators thus have serious drawbacks.
When a quartz oscillator is polished by using a polishing machine for spherical surfaces of lenses, quartz pieces are bonded together with a bonding agent. However, difficulty arises from the fact that the thickness of bonded layers are not uniform. This is liable to cause partial over-polishing and moreover it is difficult to measure the thickness of the quartz pieces.